The calcium light that Company E, 102nd NY Volunteer (a.k.a VanBuren Light) Infantry was trained to employ at the Second Battle of Charleston in September 1863 proved to be decisive.
The Calcium light had become famous on Broadway as “limelight”. The light was created by compressed hydrogen and oxygen that fed a flame directed at a “calcium oxide” lime stick. When heated to a point just before melting (4,662 °F), the lime glowed brightly. Before the Civil War, Robert Grant, of New York City, promoted the use of these calcium lights to illuminate streets and other outdoor areas. Using a parabolic mirror, he demonstrated the ability to signal ships over ten miles out to sea. At Charleston, two calcium lights were used to illuminate Fort Wagner and Battery Gregg on Morris Island from a distance of about 800yards and 1800yards respectively. The illumination prohibited the southerners from repairing damage and re-supplying the garrisons at night, not to mention strengthening the positions, which led to the eventual abandonment of the positions on the night of 6-7 September. Col. Lawrence M. Keith, commander 20th South Carolina Infantry in Battery Gregg, reported “throughout the night, the enemy light threw its bright silvery rays upon our front”, no doubt seriously complicating his life! Major Edward Manigault attempted to extinguish the lights with cannon fire from Battery Haskell on James Island but there is no record of his achieving any success. The lights allowed accurate Union artillery fire around the clock as well as protection for the Monitors off shore from torpedo craft. The lights were first used on 3 September and on 6 September the forts were abandoned.